The invention relates to an apparatus for measuring the mass of fibre material passing through a spinning preparation machine or system or through a nonwoven production device.
In a known apparatus (WO 00/12974), a carding machine is provided wherein unprocessed crude fibre material enters the carding machine at a slow speed and carded fibre material in the form of a fibre sliver or fibre web leaves the carding machine at a high speed. The carded fibre material passes through a microwave resonator, which is arranged at the exit from the carding machine and which measures the mass (density) of the fibre material. That measurement value is suitable for fine regulation of the carded fibre material, which forms an intermediate product. Furthermore, at the entrance to the carding machine there is optionally provided a measuring device for the moisture content of the unprocessed crude fibre material; this is intended to allow rough regulation. A substantial disadvantage is that rough regulation does not allow precise and uniform flows of fibre material to be accomplished in the cleaning system upstream of the carding machine. For example, the production of fibre blends having exact proportions of different fibre components is not possible using the known apparatus.
It is an aim of the invention to provide an apparatus of the kind described at the beginning that avoids or mitigates the mentioned disadvantages and, especially, that makes it possible to improve measurement of the mass of fibre material in a cleaning system, especially between a bale opener and carding machine, and to use that measurement for closed-loop and/or open-loop control.